American Indians (AIs) are experiencing an epidemic of stroke morbidity and mortality, with higher prevalence and incidence, younger age at onset, and poorer survival than other racial and ethnic groups. With a stroke incidence more than twice that of the general U.S. population, stroke in AIs is a public health problem of staggering scope. AIs also have disproportionate burdens of many risk factors for stroke, including hypertension, smoking, obesity, and diabetes. However, no rigorous, population-based studies of stroke prevention have included AIs. Tribes urgently need evidence-based methods for preventing stroke that minimize clinic visits and lab tests and use affordably measured endpoints. One such endpoint is a stroke risk score. We developed a 10-year stroke risk score for AIs using data from the Strong Heart Study, a large, population-based cohort of 4,549 AIs from 12 tribes in Arizona, Oklahoma, and the Dakotas. We propose to address the need for effective, affordable, and sustainable stroke prevention methods in participants in the Strong Heart Family Study. This study collected family-cluster data on cardiovascular disease risk factors from 3,800 AIs based on 94 randomly selected index participants from the Strong Heart Study. With our partners, we have designed the Family Intervention in the Spirit of Motivational Interviewing (FITSMI), a program delivered at the household level to encourage lifestyle changes that transform the home environment and reduce stroke risk for all residents. FITSMI uses a talking circle format in which facilitators guide participants to identify goals for change and create a tailored plan for sustainable implementation that may target smoking, exercise, diet, or medication adherence. FITSMI requires just 2 sessions (baseline and 1 month post-baseline), with text messaging used to boost long-term adherence. In a group-randomized trial design, we will recruit 360 households where Strong Heart Family Study members aged 45 and older reside. We will assign half to FITSMI and half to a control condition that receives educational brochures. All household residents e 11 years old will be eligible. Primary outcomes are household-level improvement in stroke risk score for adult's e 45 years old, and selected modifiable risk factors for all participants. Our Specific Aims are: 1) Determine the effectiveness of FITSMI in AIs e 45 years old to lower stroke risk scores from baseline to 1-year follow-up, with coronary heart disease risk scores evaluated as a secondary outcome; and 2) Determine the effectiveness of FITSMI to improve individual modifiable stroke risk factors (e.g., smoking, blood pressure) in all household members e 11 years old from baseline to 1-year follow-up. This effort is aligned with an Institute of Medicine report recommending a shift from provider- and clinic-centered healthcare to care based on continuous healing relationships. FITSMI is designed to facilitate adoption of healthy lifestyles to prevent stroke and improve cardiovascular health. If proven effective, FITSMI has broad, multigenerational public health implications for prevention of stroke and cardiovascular disease in AI and non-AI populations.